The invention relates to a rock drill having a feed direction, a helical shank and a drill head having an end face pointing in the feed direction.
Rock drills with carbide cutting tips are used for producing holes in concrete, masonry, rock or the like. In this case, the drill head, at its end face, is provided with at least one carbide cutting tip which generally extends over the entire drill head diameter and which, by the rotary-percussive or rotary-hammering drilling drive, has of a type of chiseling effect on the stone material to be disintegrated. The drill hole diameter is determined by the outside diameter of the carbide cutting tip.
In order to reduce the surface pressure on the carbide cutting tip and thus increase the service life of the drill head, cross cutting elements in which “secondary cutting tips” are arranged transversely to a main cutting tip have been disclosed (DE 29 12 394 A1).
Instead of secondary cutting tips which possibly extend over the entire diameter, secondary cutting elements which extend only over part of the radius of the drill head may also be provided (DE 81 04 116 U1).
Furthermore, EP 0 452 255 B1 has disclosed a rock drill in which the secondary cutting elements are designed as cutting pins which are arranged in the radially outer region of the end face of the drill head.
The arrangement of at least one or more additional secondary cutting tips certainly has the advantage that the main cutting tip is to a certain extent relieved of load, since some of the breaking work is assumed by the secondary cutting tip or tips. A disadvantage with this arrangement is the fact that additional fastening space has to be provided here for embedding the secondary cutting tips in the drill head, so that the end face of the drill head has to be designed to be more voluminous overall. This in turn has the disadvantage that the end face of the drill head is enlarged and forms a greater resistance. This also applies in particular to the ease with which the drill can dispose of the drillings to be removed, which collect in the direction of rotation in front of the lips of the main cutting tip and the secondary cutting tips. The quantity of these drillings increases the resistance and thus reduces the drilling advance of the drilling tool. The above problems also apply in principle to drilling tools having only a main cutting tip in which the drill head is of a less slim design and material transport thereby causes problems in the region of the drill head.
A known drilling tool has been disclosed by U.S. Pat. No. 2,673,714. In this drilling tool, an additional chip space is provided by lateral regions of the drill head being cut off in a chord-like manner in front of and behind a cutting tip, these lateral regions exposing the carbide tip in this region. A disadvantage with this is the poor embedding of the carbide tip in this region, since the recesses extend in particular on both sides of the carbide tip.